Dr. Gretz is board certified by the American Board of Obstetrics and Gynecology in gynecology, and gynecologic oncology. He received his medical degree from New York Medical College and completed an OB/GYN residency at New York University Medical Center and a fellowship in gynecologic oncology at the University of Michigan Medical Center.

He is a clinical associate professor in the Department of Obstetrics, Gynecology and Reproductive Science at Mount Sinai School of Medicine. He provides advanced surgical care, including minimally invasive and robotic procedures for benign and malignant gynecologic conditions. Some of these are fibroid uterus, endometriosis, ovarian cysts, ovarian cancer, cervical cancer and endometrial cancer. He is the former Director of Gynecologic Minimally Invasive Surgery at Mount Sinai, and Director of Gynecologic Oncology at White Plains Hospital. Dr. Gretz has published extensively and presented his research at national and international meetings.

Dr. Gretz' is affiliated with White Plains Hospital, Greenwich Hospital and The Mount Sinai Health System.